The main goal of the Phase II research is to advance the CZT detector technology in order to allow fabrication of multi-element detector arrays which can be used for dual SPECT-CT imaging. In order to achieve this goal, the research work in the Phase II project will cover several areas. Initially, the Phase II research will focus on optimization of the p-i-n design of CZT detectors in small pixel geometry. This will involve detailed investigation of electrode materials (CdS, indium, and gold) which are used for p-i-n detector fabrication. Annealing conditions for various electrodes and patterning of the electrodes for array fabrication will be investigated. Simulations of the small pixel geometry will also be carried out to determine optimal pixel size, pixel to detector thickness ratio, and inter-pixel spacing for the CZT arrays. CZT arrays will then be fabricated with p-i-n structure in small pixel geometry and their performance will be evaluated. These array modules will then be used as building blocks to assemble a large 32.4 cm x 9 mm CZT detector array for dual CT-SPECT imaging. The detector will have pixel size of 2 mm, pixel pitch of 2.25, and thickness of 5 mm. The individual array modules will be 9 x 9 mm in size and thus, 36 modules will be tiled to assemble the CT-SPECT detector. Optimized collimator for this detector will be designed and built. High performance (( electronics will also be designed in multi-channel format for reading out signal from the CZT detector pixels. Finally, the CZT detector array, collimator, and readout electronics assembly will be sent to University of California, San Francisco (UCSF) where the collaborators will evaluate its performance in simultaneous SPECT-CT neuroimaging.